Systems and methods to connect sintered aluminum electrodes of an energy storage device

ABSTRACT

This document provides an apparatus including a sintered electrode, a second electrode and a separator material arranged in a capacitive stack. A conductive interconnect couples the sintered electrode and the second electrode. Embodiments include a clip interconnect. In some embodiments, the interconnect includes a comb-shaped connector. In some embodiments, the interconnect includes a wire snaked between adjacent sintered substrates.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/521,660, filed on Oct. 23, 2014, now issued as U.S. Pat. No.9,424,997, which is a continuation of U.S. patent application Ser. No.12/968,571, filed on Dec. 15, 2010, now issued as U.S. Pat. No.8,873,220, which claims the benefit of U.S. Provisional Application No.61/288,095, filed on Dec. 18, 2009, under 35 U.S.C. §119(e), each ofwhich is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This document relates generally to energy storage and particularly tosintered electrodes to store energy in an implantable medical device.

BACKGROUND

Electrical stimulation therapy has been found to benefit some patients.For example, some patients suffer from an irregular heartbeat orarrhythmia and may benefit from application of electrical stimulation tothe heart. Some patients suffer from a particular type of arrhythmiacalled a fibrillation. Fibrillations may affect different regions of theheart, such as the atria or the ventricles. When a fibrillation occursin the ventricles, the heart's ability to pump blood is dramaticallyreduced, putting the patient at risk of harm. It has been found thatapplying an electrical stimulation to the patient can effectively treatpatients suffering disorders such as from fibrillation by restoring aregular heartbeat.

Because disorders such as fibrillations can happen at any time, it ishelpful to have a device that is easily accessible to treat them. Insome cases, it is helpful if that device is portable or implantable. Indeveloping a device that is portable or implantable, it is helpful tohave access to subcomponents that are compact and lightweight and thatcan perform to desired specifications.

SUMMARY

This disclosure relates to apparatus for coupling sintered electrodes ofan energy storage device. An apparatus according to one embodimentincludes an electrode including a sintered material deposited on aconductive substrate, the conductive substrate having a substrateflexibility greater than a material flexibility of the material, thesubstrate including a substrate connection portion, a separator disposedin a capacitor stack with the electrode in alignment, a second electrodedisposed in the capacitor stack in alignment, the second electrodeincluding a connection portion, and a conductive interconnect physicallyand electrically coupling the substrate connection portion and theconnection portion of the second electrode, the substrate connectionportion and the connection portion of the second electrode adapted todeform to accommodate displacement of the electrode with respect to thesecond electrode. An embodiment includes a slotted interconnect.Additional embodiments include a interconnect comprising a wire snakedbetween two sintered substrates.

This Summary is an overview of some of the teachings of the presentapplication and not intended to be an exclusive or exhaustive treatmentof the present subject matter. Further details about the present subjectmatter are found in the detailed description and appended claims. Otheraspects of the invention will be apparent to persons skilled in the artupon reading and understanding the following detailed description andviewing the drawings that form a part thereof. The scope of the presentinvention is defined by the appended claims and their legal equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate generally, by way of example, variousembodiments discussed in the present document. The drawings are forillustrative purposes only and may not be to scale.

FIG. 1 is a schematic of a medical system including a sinteredcapacitor, according to some embodiments.

FIG. 2 is an implanted medical system including a sintered capacitor,according to some embodiments.

FIG. 3 shows a capacitor element according to an embodiment of thepresent subject matter.

FIG. 4 shows a capacitive element according to an embodiment of thepresent subject matter.

FIG. 5 shows a capacitive element according to an embodiment of thepresent subject matter.

FIGS. 6A and 6B show a capacitive element according to embodiments ofthe present subject matter.

FIG. 7 shows a capacitor element according to an embodiment of thepresent subject matter.

FIG. 8 shows a capacitive element according to an embodiment of thepresent subject matter.

FIG. 9A shows an exploded view of a capacitive element according to anembodiment of the present subject matter.

FIG. 9B shows a cross-section of anode components according to anembodiment of the present subject matter.

FIG. 9C shows a sintered pattern according to an embodiment of thepresent subject matter.

DETAILED DESCRIPTION

The following detailed description of the present invention refers tosubject matter in the accompanying drawings which show, by way ofillustration, specific aspects and embodiments in which the presentsubject matter may be practiced. These embodiments are described insufficient detail to enable those skilled in the art to practice thepresent subject matter. References to “an”, “one”, or “various”embodiments in this disclosure are not necessarily to the sameembodiment, and such references contemplate more than an embodiment. Thefollowing detailed description is, therefore, not to be taken in alimiting sense, and the scope is defined only by the appended claims,along with the full scope of legal equivalents to which such claims areentitled.

Energy storage capacitors are used with implantable devices to providestimulation energy. Advances continue to take place to increase theenergy storage of such capacitors while also reducing the size of thecapacitors. As these advances take place they present new challenges forefficiently and economically producing the more advanced energy storagecapacitors. The present disclosure relates to energy storage devicesthat include flexible foil substrates and interconnects to couplemultiple substrates together. The flexible foil substrates provide amore robust material for handling and coupling electrodes over energystorage devices using etched electrodes. The flexible foil substratesprovide give under pressure and may be bent as they are assembled andcoupled, whereas etched materials often break under light bendingpressure.

FIG. 1 is a schematic of a medical system 100 including a flexible foilcapacitor, according to some embodiments. The medical system 100represents any number of systems to provide therapeutic stimulus, suchas to a heart. Examples of medical systems include, but are not limitedto, implantable pacemakers, implantable defibrillators, implantablenerve stimulation devices and devices that provide stimulation fromoutside the body, including, but not limited to, externaldefibrillators.

Electronics 104 are to monitor the patient, such as by monitoring asensor 105, and to monitor and control activity within the system 100.In some examples, the electronics 104 are to monitor a patient, diagnosea condition to be treated such as an arrhythmia, and control delivery ofa stimulation pulse of energy to the patient. The electronics 104 can bepowered wirelessly using an inductor. Alternatively, the electronics 104can be powered by a battery 106. In some examples, electronics 104 areto direct small therapeutic bursts of energy to a patient from thebattery 106.

For therapies, such as defibrillation, that use energy discharge ratesexceeding what battery 106 is able to provide, a capacitor 108 is used.Energy from the battery 106 is controlled by the electronics 104 tocharge the capacitor 108. The capacitor 108 is controlled by theelectronics 104 to discharge to a patient to treat the patient. In someexamples, the capacitor 108 completely discharges to a patient, and inadditional examples, the capacitor is switched on to provide therapeuticenergy and switched off to truncate therapy delivery.

Some examples of a medical system 100 include an optional lead system101. In certain instances, after implantation, the lead system 101 or aportion of the lead system 101 is in electrical communication withtissue to be stimulated. For example, some configurations of lead system101 contact tissue with a stimulation electrode 102. The lead system 101couples to other portions of the system 100 via a connection in a header103. Examples of the system 101 use different numbers of stimulationelectrodes and/or sensors in accordance with the needs of the therapy tobe performed.

Additional examples function without a lead 101. Leadless examples canbe positioned in contact with the tissue to be stimulated, or can bepositioned proximal to tissue to shock the tissue to be stimulatedthrough intermediary tissue. Leadless examples can be easier to implantand can be less expensive as they do not require the additional leadcomponents. The housing 110 can be used as an electrode in leadlessconfigurations.

In certain embodiments, the electronics 104 include an electroniccardiac rhythm management circuit coupled to the battery 106 and thecapacitor 108 to discharge the capacitor 108 to provide a therapeuticdefibrillation pulse. In some examples, the system 100 includes an anodeand a cathode sized to deliver a defibrillation pulse of at leastapproximately 50 joules. Other configurations can deliver larger amountsof energy. Some configurations deliver less energy. In some examples,the energy level is predetermined to achieve a delivered energy levelmandated by a governing body or standard associated with a geographicregion, such as a European country. In an additional embodiment, theanode and cathode are sized to deliver a defibrillation pulse of atleast approximately 60 joules. In some examples, this is the energylevel is predetermined to achieve an energy level mandated by agoverning body of another region, such as the United States. In someexamples, electronics 104 are to control discharge of a defibrillationpulse so that the medical system 100 delivers only the energy mandatedby the region in which the system 100 is used. In some examples, a pulseof 36 joules is delivered.

Packaging anodes and cathodes can reduce their efficiency.Interconnections between conductors coupled to electronics and to theelectrodes of the capacitor 108 decrease efficiency, for example.Accordingly, anodes and cathodes are sized to compensate for decreasesin efficiency. As such, in some embodiments, the capacitor 108 includesanodes and cathodes sized and packaged to deliver a defibrillation pulseof at least approximately 50 joules. Some are sized and packaged todeliver a defibrillation pulse of at least approximately 60 joules.

One characteristic of some sintered electrode examples is that at leastone anode and a cathode have a DC capacitance that is approximately 23%greater than a AC capacitance for the at least one anode and the cathodeof an etched capacitor that has 74.5 microfarads per cubic centimeter.In some examples, the at least one anode and the cathode have an ACcapacitance of at least 96.7 microfarads per cubic centimeter at 445total voltage. In some examples, this is comparable to an operatingvoltage of about 415 volts. This is a 30% improvement over an etchedcapacitor that has 74.5 microfarads per cubic centimeter. Total voltageis the voltage that allows 1 milliamp of leakage per square centimeter.Some examples are aged to 415 volts.

In certain examples, the capacitor 108 includes a capacitor case 112sealed to retain electrolyte. In some examples, the capacitor case 112is welded. In some instances, the capacitor case 112 is hermeticallysealed. In additional examples, the capacitor case 112 is sealed toretain electrolyte, but is sealed with a seal to allow flow of othermatter, such as gaseous diatomic hydrogen or a helium molecule. Some ofthese examples use an epoxy seal.

A hermetically sealed device housing 110 is used to house components,such as the battery 106, the electronics 104, and the capacitor 108.Hermeticity is provided by welding components into the hermeticallysealed device housing 110, in some examples. Other examples bondportions of the housing 110 together with an adhesive such as a resinbased adhesive such as epoxy. Accordingly, some examples of the housing110 include an epoxy sealed seam or port. Several materials can be usedto form housing 110, including, but not limited to, titanium, stainlesssteel, nickel, a polymeric material, or combinations of these materials.In various examples, the housing 110 and the case 112 are biocompatible.

The capacitor 108 is improved by the present electrode technology inpart because it can be made smaller and with less expense. Theimprovement provided by these electrodes is pertinent to applicationswhere high-energy, high-voltage, or space-efficient capacitors aredesirable, including, but not limited to, capacitors used forphotographic flash equipment. The present subject matter extends toenergy storage devices that benefit from high surface area sinteredelectrodes including, but not limited to, aluminum. The electrodesdescribed here can be incorporated into cylindrical capacitors that arewound, in addition to stacked capacitors.

FIG. 2 is an implanted medical system 200, implanted in a patient 201,and including a sintered capacitor, according to some embodiments. Thesystem includes a cardiac rhythm management device 202 coupled to afirst lead 204 to extend through the heart 206 to the right ventricle208 to stimulate at least the right ventricle 208. The system alsoincludes a second lead 210 to extend through the heart 206 to the leftventricle 212. In various embodiments, one or both of the first lead 204and the second lead 210 include electrodes to sense intrinsic heartsignals and to stimulate the heart. The first lead 204 is in directcontact (e.g., touching) with the right atrium 214 and the rightventricle 208 to sense and/or stimulate both those tissue regions. Thesecond lead 210 is in direct contact with the left atrium 216 and theleft ventricle 212 to sense and/or stimulate both those tissue regions.The cardiac rhythm management device 202 uses the lead electrodes todeliver energy to the heart, either between electrodes on the leads orbetween one or more lead electrodes and the cardiac rhythm managementdevice 202. In some examples, the cardiac rhythm management device 202is programmable and wirelessly communicates 218 programming informationwith a programmer 220. In some examples, the programmer 220 wirelessly218 charges an energy storage device of the cardiac rhythm managementdevice 202.

The capacitor includes an anode and a cathode separated by a dielectric.The capacitor may be coupled to electronics adapted to charge thecapacitor and use the energy for various purposes such as deliveringtherapy via an implantable medical device. In various embodiments, thecapacitor includes one or more sintered anode layers. In someembodiments, the anode layers are electrically coupled together toprovide a desired energy density.

FIG. 3 shows a capacitor element according to an embodiment of thepresent subject matter. The capacitor element 330 includes a number ofelectrodes, including a number of cathode stacks 337 and a number ofanode layers 338. In various embodiments, the electrodes include foil,such as an aluminum foil. Cathode stacks 337 include a cathode includinga cathode foil, such as a flexible foil in some embodiments. In variousembodiments, the cathode stack 337 includes separator material disposedbetween the cathode foil and adjacent anode layers. The separatormaterial may include electrolyte in some embodiments. In the illustratedembodiment, the anode layers include a sintered material. The sinteredanode layers include a sintered material 339 disposed on a foilsubstrate 340. The foil provides a more robust electrode than, forexample, an etched electrode, because the foil is more flexible and,thus more resistant to breaking when bent or folded. In variousembodiments, the foil is more flexible than the sintered material. Theflexible substrate may deform substantially more than an etchedsubstrate to accommodate displacement between connected componentsduring manufacturing as well as throughout the life of the capacitorelement. Deformability of foil-based electrodes provide bettermanufacturing yields and reduces component failures over etched basedelectrodes. A tab 341 is coupled to each anode substrate 340 and thetabs 341 are connected together. In various embodiments, the tabs 341may be continuous portions of the anode substrate 340. In someembodiments, the tab 341 may include a portion of the anode substrateand a separate conductive material coupled to the portion of the anodesubstrate. Some embodiments may include a separate conductive materialcoupled to the anode substrate to form the tab 341. In variousembodiments, the cathode stacks include foil. In such embodiments, aclip may be used to couple the cathode stacks together, bothmechanically and electrically. In the illustrated embodiment, thecapacitive element is shown in an exploded view.

The tabs 341 are gathered and coupled together in a clip 345. A clip 345is used to couple the tabs together. In various embodiments, the tabs341 may be gathered and coupled together, such as by welding orsoldering, prior to assembly into the clip 345. In some embodiments, thetabs 341 are secured with the clip 345 using one or more techniques suchas crimping, welding or soldering. The clip 345 may be used to coupleelectrodes to other capacitor elements such as, a case, a feedthrough,other electronics, other electrode, other electrode groups, orcombinations thereof. In various embodiments, the clip is to crimp tabstogether. In some examples, the clip is elastically deformed to couplethe tabs to one another. In additional embodiments, the clip isinelastically deformed to couple the tabs. In some examples, the clip iscold welded to one or more tabs. In some examples, the clip is alignedto one or more tabs. In various embodiments, an electrode may includemultiple tabs. Such a configuration allows for various capacitor elementconnection schemes including, for example, to partition a capacitorstack into two or more capacitive elements.

FIG. 4 shows a capacitive element according to an embodiment of thepresent subject matter. The capacitive element 430 includes a number ofelectrodes including a number of cathode stacks 437 and a number ofsintered anode layers 438. A cathode stack includes a cathode layer, thesintered anode layers include a sintered material 439 disposed on asubstrate 440, such as a flexible foil substrate. In some examples, thesintered material 429 is sintered onto the substrate 440. A tab 441 iscoupled to each anode substrate 440 and the tabs 441 are coupledtogether. The tabs 441 are coupled together using a clip 445 coupled toeach tab 441. In some embodiments, the electrode does not include a taband the clip couples to a sinter-free portion of the substrate. Theclips 445 are coupled together using a weld for example. It understoodthat other methods of coupling the clips together are possibleincluding, but not limited to, mechanical coupling, cold welding, laserwelding, ultrasonic welding, or combinations thereof. Such couplingmethods may be used to couple the tabs 441 to the clips 445, as well as,crimping the tabs in the clips.

In various embodiments, clips are coupled to other components, forexample, other capacitive elements. In some examples, a plurality ofclips are coupled together, then coupled to a second component. Inadditional embodiments, at least one clip is individually coupled toanother component. In some of these embodiments, a plurality of layersare placed into electrical communication via the other component. Othercomponents include, but are not limited to, tabs, feedthroughs,terminals, and other conductive materials. In the illustratedembodiment, the clips 445 are coupled to a case 443 enclosing thecapacitive element 430. A ribbon of conductive material 446, or a wire,may be used to couple the clips 445 to the case 443. In variousembodiments, the clips may be directly coupled to the case.

FIG. 5 shows a capacitive element according to an embodiment of thepresent subject matter. The capacitive element 530 includes a number ofcathode stacks 537 and a number of sintered anode layers 538. Thesintered anode layers include a sintered material 539 disposed on asubstrate 540. A tab 541 is coupled to each anode substrate 540 and thetabs 541 are connected together. The tabs 541 are coupled together usinga clip 545 coupled to each tab 541. The clips 545 are coupled togetherusing a weld for example. Other methods of coupling the clips togetherare possible, including, but not limited to, mechanical coupling, suchas by a pin, cold welding, laser welding, ultrasonic welding, orcombinations thereof. Such coupling methods may be used to couple thetabs to the clips. Crimping the tabs in the clips is also another methodthat may be used in some embodiments.

In various embodiments, the set of coupled clips are coupled to othercomponents, for example, other capacitive elements. In the illustratedembodiment, the clips 545 are coupled to a feedthrough 547 of a case 543enclosing the capacitive element 530. A ribbon of conductive material546, or a wire, may be used to couple the set of clips 545 to thefeedthrough 547. In some embodiments, the clips are coupled to a caseenclosing the capacitive elements. In various embodiments, the clips maybe directly coupled to the case.

FIG. 5 shows the stack of anode layers 538 and cathode stacks 537 in anexploded view. In various embodiments, the clips 545 are sized such thatthe separation between each clip slot is substantially the same as theseparation of adjacent anode layers in the assembled stack. Configuringthe clips as such reduces stress on the electrode tabs. This can extendthe life of the capacitor by reducing the number of instances of tabbreakage.

FIGS. 6A and 6B show a capacitive element according embodiments of thepresent subject matter. The capacitive element 630 of FIG. 6A shows anumber of electrodes including a number of cathode stacks 637 and anumber of anode layers 638 stacked to form the capacitive element 630.Cathode stacks 637 may include a cathode foil, such as a flexible foilin some embodiments. In various embodiments, the cathode stack 637includes separator material disposed between the cathode foil andadjacent anode layers. The separator material may include electrolyte insome embodiments.

The anode layers 638 include a sintered material 639 deposited on asubstrate 640, such as a flexible foil substrate. In variousembodiments, the sintered material 639 and the substrate 640 includealuminum. The anode layers 638 include a tab 641 extending from thelayer. In various embodiments, the tab 641 is a continuous, monolithicand solid portion of the anode substrate 640. In some embodiments, thetab includes a separate piece of material coupled to the anode layer.

Also shown in the embodiment of FIG. 6A is an interconnect 660 to couplethe tabs 641 of the anode layers together. The interconnect 660 includesa series of slots 661, with the interconnect defining a comb shape. Insome examples, the slots 661 are spaced apart to substantially match theseparation of the tabs 641 extending from the anode layers. After a tabis positioned in a slot of the connector, the tab is coupled to theconnector. Methods of coupling the tab to the connector include, but arenot limited to, welding, soldering, crimping, or combinations thereof.

FIG. 6B shows a slotted, comb-type interconnect 660 coupled to the tabs641 of a capacitor element 630 where the interconnect 660 is oriented 90degrees from that shown in FIG. 6A. Other orientations of theinterconnect are possible without departing from the scope of thepresent subject matter. Various orientations may be better adapted tothe shape of a particular capacitor element or the space availablewithin a case enclosing the capacitor element, or combinations thereof.

FIG. 7 shows a capacitor element according to an embodiment of thepresent subject matter. The capacitor element 730 includes a number ofcathode stacks 737 and a number of sintered anode layers 738 stackedtogether. The anode layers 738 include a sintered material 739 depositedon a substrate 740, such as a foil. Anode tabs 741 extend from thesubstrate 740. The anode tabs 741 are coupled together using a slottedinterconnect 760. The slots 761 of the slotted interconnect 760 arespaced to substantially match the separation of the anode layers 738,thus minimizing stress on the tabs and, in some instances, reducing thechance of damaging the anode tab or substrate. In various embodiments,the slotted interconnect is coupled to a case enclosing the capacitorelement. The anodes of the illustrated capacitive element are coupled toa case 743 using a ribbon of conductive material 746. Methods ofcoupling the ribbon of conductive material to the case include, but arenot limited to, welding soldering, mechanical coupling such as bycrimping, or combinations thereof.

FIG. 8 shows a capacitive element according to an embodiment of thepresent subject matter. The capacitive element 830 includes a number ofelectrodes including a number of cathode stacks 837 and a number ofanode layers 838 stacked to form the capacitive element 830. Eachcathode stack 837 includes a cathode foil. In various embodiments, acathode stack 837 includes separation material disposed between thecathode foil and adjacent anodes. In some embodiments, the separationmaterial includes electrolyte. The anode layers 838 include a sinteredmaterial 839 disposed on a substrate 840.

Anode tabs 841 extend from each anode layer. The anode tabs 841 arecoupled together using a slotted comb-type interconnect 860. Multipleanode tabs 841 may be coupled in a slot 861 of the slotted interconnect860. The illustrated embodiment, shows pairs of tabs 841 gathered andcoupled in each slot 861 of the slotted interconnect 860. In certainexamples, each slot of the slotted interconnect may have other numbersof anode tabs coupled together. The slotted interconnect 860 is coupledto a feedthrough 847 of a case 843 enclosing the capacitive element 830.

In some embodiments, the interconnect 860 may be directly coupled to thefeedthrough 847. In the illustrated embodiment, the slotted interconnect860 is coupled to the feedthrough 847 using a ribbon of conductivematerial 846. Such a configuration may allow the anodes to be insulatedfrom the case, and may allow the anodes to be coupled with otherelectronics, such as electronics of an implantable medical device.

FIG. 9A shows an exploded view of a capacitive element according to anembodiment of the present subject matter. The capacitive element 930includes a number of cathode stacks 937 and a number of anode components970 stacked to form the capacitive element 930. The cathode stacks 937include a cathode foil. In various embodiments, the cathode stacksinclude a separator material disposed between the cathode foil andadjacent anode components. In some embodiments, the separator materialincludes electrolyte. The anode components 970 include two anode layers938 with a wire 971 snaked between them. Each anode layer includessintered material 939 disposed on a substrate 940, such as a foil. FIG.9B shows a cross-section of the anode components 970. Each anodeincludes a pattern of sintered material 939 on one side of the substrate940.

The anode layers 938 are stacked such that the sinter-free sides if eachanode substrate 940 is proximate the other. A wire 971, or ribbon ofconductive material, is disposed between the anode layers 938. In someexamples, the wire 971 is disposed at least partially into the stack,with a substrate connection portion 941 (FIG. 9C) bunched around thewire 971. In some examples, a connection portion of a second electrodeis bunched around the conductive interconnect. In some examples, thesubstrate connection portion 941 and the connection portion of thesecond electrode conformed to the conductive interconnect. The wire 971assists lateral charge migration in the capacitive element thus reducingthe equivalent series resistance (ESR) of the capacitive element.

FIG. 9C shows a sintered pattern according to an embodiment of thepresent subject matter. FIG. 9C also shows the location of a wire path972 between the anode layers 938. Note that the wire path proceedsthrough areas where the substrate is free of sintered material. Thisallows the wire 971 to be disposed in a recess formed between the anodelayers 938 without creating a bulge that effects the stacking ofadditional capacitor element components. It is understood that othersintered patterns are possible without departing from the scope of thepresent subject matter.

In various embodiments, an anode layer 938 includes a recess 973 toprovide access to the wire 971 or conductive ribbon of material. In someembodiments, the wire 971, or conductive ribbon of material, extendsfrom the anode layers 938 for coupling with other components such asother anode layers. In such embodiments, the extending wire, or ribbonof conductive material, is akin to the anode tabs described above. Assuch, the anodes may be connected together using a weld, using a clip,using a slotted connector, or combination thereof. Additionally, theanodes may be coupled to a case, or a feedthrough extending through thecase.

This application is intended to cover adaptations or variations of thepresent subject matter. It is to be understood that the abovedescription is intended to be illustrative and not restrictive. Thescope of the present subject matter should be determined with referenceto the appended claims, along with the full scope of legal equivalentsto which such claims are entitled.

What is claimed is:
 1. An apparatus comprising: a cathode; a separatorstacked in alignment with the cathode; an anode assembly disposed in astack with the cathode and the separator, the separator disposed betweenthe cathode and the anode assembly to physically separate the cathodeand the anode assembly, wherein the anode assembly includes: a firstlayer including a first sintered material deposited on a firstsubstrate; a second layer stacked with the first layer, the second layerincluding a second sintered material deposited on a second substrate,wherein the first substrate of the first layer and the second substrateof the second layer are proximate each other and between the firstsintered material and the second sintered material; and an interconnectcoupled to the first substrate and the second substrate to electricallycouple the first layer and the second layer of the anode assembly,wherein the interconnect includes a conductive element disposed betweenthe first substrate and the second substrate, and wherein the firstsubstrate and the second substrate are substantially sinter-free along apath of the conductive element.
 2. The apparatus according to claim 1,wherein the interconnect includes a wire snaked between the first layerand the second layer.
 3. The apparatus of claim 1, wherein theinterconnect includes a conductive ribbon snaked between the first layerand the second layer.
 4. The apparatus of claim 1, wherein a sinter-freeside of each anode substrate is proximate the other.
 5. The apparatus ofclaim 4, wherein the interconnect path proceeds through areas where thesubstrates are free of sintered material.
 6. The apparatus of claim 1,wherein the first and second substrates have a flexibility greater thana material flexibility of the sintered material.
 7. The apparatus ofclaim 1, wherein the interconnect coupled to the first substrate and thesecond substrate physically and electrically couples the first layer andthe second layer of the stack.
 8. The apparatus of claim 7, wherein thefirst layer includes a first tab extending from a first location along aperimeter of the first layer.
 9. The apparatus of claim 8, wherein thefirst layer includes a second tab extending from a second location,other than the first location, along the perimeter of the first layer.10. The apparatus of claim 8, wherein the second layer includes a secondtab extending from the first location along a perimeter of the secondlayer, and wherein the first tab is coupled to the second tab using theinterconnect.
 11. The apparatus of claim 10, including a weld to couplethe first tab with the second tab.
 12. The apparatus of claim 11, whereat least one of the first layer and the second layer includes a notchconfigured to expose the conductive element disposed between the firstsubstrate and the second substrate.